1. Field of the Invention
This invention relates to an information recording-reproducing apparatus in which an information recording medium and a recording-reproducing head are moved relative to each other to thereby accomplish recording and/or reproduction of information, and in particular to an information recording-reproducing apparatus in which the velocity at which the information recording medium is moved is stabilized and made constant.
2. Related Background Art
The forms of the information recording medium include a disk-like one (such as a magnetic disk, an optical disk or a magneto-optical disk), a tape-like one (such as a magnetic tape or an optical tape) and a card-like one (such as a magnetic card or an optical card). Among these, the card-like information recording medium (hereinafter simply referred to as the card) is finding wider use because of its excellence in accessibility, ease of manufacture and portability, and particularly, optical type optical cards permit highly dense recording and have therefore been actively studied in recent years. The case of the card will hereinafter be described as an example.
In an information recording-reproducing apparatus using such a card, the card is reciprocally moved relative to a recording-reproducing head to thereby scan the data track of the card and accomplish recording reproduction of information.
FIGS. 1(A) and (B) of the accompanying drawings illustrate the operation of a card driving mechanism in an information recording-reproducing apparatus according to the prior art.
In these Figures, drive rollers 5a, 5b and 5c are rotated in a predetermined direction and at a predetermined speed by driving means, not shown, and pressing rollers 6a, 6b and 6c biased by bias means press the drive rollers 5a, 5b and 5c with suitable pressure. Hereinafter, the drive roller 5a and the pressing roller 6a will be referred to as a pair of rollers a, and the set of roller 5b and 6b and the set of roller 5c and 6c will likewise be referred to as a pair of rollers b and a pair of rollers c, respectively.
The card 1 is nipped between the pair of rollers a, b or c and reciprocally moved by roy reproduction of information.
FIGS. 1(A) and (B) of the accompanying drawings illustrate the operation of a card driving mechanism in an information recording-reproducing apparatus according to the prior art.
In these Figures, drive rollers 5a, 5b and 5c are rotated in a predetermined direction and at a predetermined speed by driving means, not shown, and pressing rollers 6a, 6b and 6c biased by bias means press the drive rollers 5a, 5b and 5c with suitable pressure. Hereinafter, the drive roller 5a and the pressing roller 6a will be referred to as a pair of rollers a, and the set of roller 5b and 6b and the set of roller 5c and 6c will likewise be referred to as a pair of rollers b and a pair of rollers c, respectively.
The card 1 is nipped between the pair of rollers a, b or c and reciprocally moved by rotation of those rollers, and recording reproduction of information is effected by a recording-reproducing head, not shown. However, the length of the card 1 in the direction in which it is reciprocally moved is L.sub.1, the interval between the drive rollers 5 and between the pressing rollers 6 is L.sub.2, and L.sub.1 and L.sub.2 are in the relation that L.sub.1 &gt;L.sub.2.
The above described example of the prior art, however, has suffered from a problem that the card 1 cannot be stably moved at a predetermined velocity.
In the above-described example of the prior art, let it be assumed that, as shown in FIG. 1(A), the card 1 is being moved in the direction of arrow B' while being nipped between the pairs of rollers a and b. In this state, the card 1 is being moved at a predetermined velocity conforming to the speed of rotation of each roller.
However, since L.sub.1 &gt;L.sub.2, the leading end of the card 1 is nipped between the pair of rollers c as shown in FIG. 1(B) and at that time, the movement velocity of the card 1 unavoidably fluctuates greatly. Also, where each pair of rollers are rotated in the opposite direction to move the card 1 in the direction opposite to the direction of arrow B', similar fluctuation of the velocity will occur when the leading end of the card 1 is nipped between the pair of rollers a.
If the velocity of the card 1 thus fluctuates suddenly, it will become impossible to accomplish proper recording and reproducing operations and the reliability as an information recording-reproducing apparatus will be greatly reduced. Particularly, in an optical type information recording-reproducing apparatus, a minute light spot is formed and highly dense recording is effected at a high speed and therefore, such instability of the operation must be avoided to the utmost.
Also, recording and reproducing operations can be accomplished with the velocity fluctuation area being avoided, but in such case, the information recording capacity decreases correspondingly and therefore, such means of solution cannot be adopted.